1. Field of the Invention
The present invention is directed to an axial torque governor for a turbo-supercharger for an internal combustion engine comprising a radial compressor composed of an axial diffusor and comprising a collar of guide vanes extending radially relative to the supercharger axis and pivotable around radially-directed swiveling axes, the guide vanes being arranged in a flow channel in a housing whose inner wall, as seen in the flow direction, comprises a first jacket of a cylindrical section and a jacket of a spherical section, and adjustment levels arranged on the shafts of the guide vanes and projecting out along the pivoting axes, the adjustment levers engaging into an adjustment ring which concentrically closes the housing.
2. Description of the Prior Art
Turbo-superchargers are employed in internal combustion engines in order to increase the power and torque given favorable fuel consumption. Since, due to their pressure-volume characteristic, turbo-superchargers comprising a radial flow compressor are not capable of covering the entire operating range of the internal combustion engine, operating conditions which lie to the left of the surge or, respectively, flow-disruption limit of the compressor performance characteristics can occur, first of all, given low engine speed and a full-load operation and, secondly, operating conditions which lie to the right of the tamping limit of the compressor performance characteristics can occur given high engine speeds and full-load operation. For this reason, it is standard to design turbo-superchargers such that the surge or, respectively, flow-disruption limit is not crossed toward the left given lower engine speeds as well as a partial load or, respectively, flow-load operation. For example, the German published application No. 14 26 076 discloses bypass valves at the turbine side for the control of this operating behavior, a portion of the exhaust stream being capable of being conducted around the turbine with assistance of the bypass valves in order to avoid high boost pressures given full load and high speed. A portion of the energy of the exhaust is lost, unused, in this control.
Another control at the turbine side is realized by an adjustable nozzle scroll in accordance with the German published application No. 24 55 361, whereby the exhaust gas can be better utilized.
In general, however at the turbine side for turbo-superchargers only influence the power or, respectively, the torque. They are suitable for adapting a momentary power consumption of the compressor to the requirements within the limits established by the available quantity of exhaust gas and by the temperature of the exhaust gas. They thereby bury the mass flow, but not the compressor performance characteristics. As a consequence thereof, it is definitely possible that the compressor operating point migrates out of the region of good efficiency, or can even end up in the surge region.
The German published application No. 14 26 076 also discloses a turbo-supercharger control at the compressor side, whereby the volume stream can be reduced, in fact can even be entirely suppressed by way of a throttle valve in the suction region. A suppression of the volume flow can be desirable for example, given a temporary disengagement of the engine, for example when disengaging the clutch, in order to provide that the compressor no longer takes any power and the rotor of the turbo-supercharger does not all too greatly decrease in speed. Moreover, a modification of the usable range of performance characteristics is not possible with this turbo-supercharger governor at the compressor site.
The German application No. 16 28 232 discloses an axial torque governor for compressors having larger dimensions with which a shift in characteristics is possible. In this axial torque governor, the flow channel in which the guide vanes of the axial inlet passage are arranged is composed of two cylindrical jacket sections having diameters differing only slightly and on the spherical section lying there between, whereby the radius of the sphere is larger than the radius of the larger cylindrical jacket section, i.e. the flow channel experiences an increase in diameter in the region of the guide vanes. This increase in diameter in the flow channel leads to a burbling and to an increase in the trailing vortex caused by the discontinuity in speed at the guide vanes. Since the cylindrical jacket section following the spherical section at the compressor side has only an insignificantly smaller diameter than the first cylindrical jacket section, a rapid suppression in the disturbance of the flow before entry into the compressor is not possible.